1. Field of the Invention
The present invention relates to a semiconductor manufacturing technique and, more particularly, to a technique which is advantageously applied to high output MOSFETs (metal oxide semiconductor field effect transistors).
2. Description of the Prior Art
According to a study made by the inventor, exemplary semiconductor devices that generate high output and high heat include transistors referred to as xe2x80x9cMOSFETsxe2x80x9d which are used in electronic and electric apparatuses in all fields including power supplies and switches of battery-driven apparatuses, car electronics and controllers for driving motors.
An example of such MOSFETs that generate high output and high heat is disclosed in Japanese unexamined patent publication No. H8-64634. The MOSFET comprises a semiconductor pellet on which a field effect transistor (MOSFET element) is formed in a compact and plate-like configuration, a plurality of inner leads electrically connected to a surface electrode of the semiconductor pellet for electrically conducting the MOSFET element to the outside, a header for improving radiating performance and resin encapsulant formed by encapsulating the semiconductor pellet, the inner leads and a part of the header with resin. Each of the inner leads is mechanically and electrically connected through protruding terminals to a principal surface of the semiconductor pellet which is a circuit forming surface, and the header is bonded to a back surface of the semiconductor pellet which is the surface opposite to the principal surface.
In this MOSFET, since each of the inner leads is electrically connected to the surface electrode of the semiconductor pellet through the protruding terminals, external resistance is lower than that in the case of electrical connection using bonding wires. Further, since the header is separate from the inner leads, the header can be formed using a material having preferable radiating performance irrespective of the material of the inner leads, which makes it possible to improve the radiating performance of the header.
In the above-described MOSFET, the sum of electrical resistance of bonding wires, electrical resistance of aluminum wiring on the semiconductor pellet (hereinafter referred to as xe2x80x9cexternal resistancexe2x80x9d) and resistance inside the semiconductor pellet (hereinafter referred to as xe2x80x9cinternal resistancexe2x80x9d) is the on resistance of the MOSFET as a whole. Substantially no problem is caused by the external resistance when the internal resistance is high.
However, when the magnitude of the external resistance exceeds about 50% of the entire resistance as a result of technical advances toward improvements to reduce the internal resistance, situations occur wherein the external resistance is not negligible.
In the above-described MOSFET, since each of the inner leads is electrically connected to the surface electrode of the semiconductor pellet through the protruding terminals, the external resistance can be lower than that in the case of electrical connection using bonding wires. However, since an outer lead connected to each of the inner leads becomes long accordingly, there is a corresponding reduction of the effect of reducing the external resistance.
It is an object of the invention to provide a semiconductor device in which the external resistance can be significantly reduced and a method of manufacturing the same.
It is another object of the invention to provide a semiconductor device whose thermal resistance and packaging height can be reduced and a method of manufacturing the same.
The above and other objects and novel features of the invention will become apparent from the description of the present specification and the accompanying drawings.
According to the present invention, there is provided a semiconductor device comprising:
a semiconductor pellet having a field effect transistor fabricated on a principal surface thereof and formed in a compact and plate-like configuration;
a plurality of inner leads for electrically conducting the field effect transistor element to the outside;
outer leads connected to the respective inner leads;
a header for improving radiating performance; and
a resin encapsulant for resin-encapsulating the inner leads and a part of the header, wherein
each of the inner leads is mechanically and electrically connected to the principal surface of the semiconductor pellet with a connecting portion constituted by a protruding terminal;
the header exposed from the resin encapsulant is mechanically and electrically connected to a surface of the semiconductor pellet opposite to the principal surface; and
each of the outer leads is bent in a gull wing configuration.
As a result, since an inner lead coupling portion for supporting each of the inner leads is directly connected to the semiconductor pellet by the respective connecting portion, external resistance can be lower than that in the case of electrical connection using bonding wires.
Since the outer leads formed in a gull wing configuration and the header mechanically and electrically connected to the semiconductor pellet can be surface-mounted on a printed circuit board, a further reduction of external resistance can be achieved.
Since the header is separate from the inner leads, the radiating performance of the header can be improved by forming it using a material having preferable radiating performance irrespectively of the material of the inner leads. Further, since the header is surface-mounted on a printed circuit board, heat from the semiconductor pellet can be effectively released to the printed circuit board as a result of thermal conduction, which makes it possible to improve the radiating performance further.
According to the invention, there is provided a semiconductor device comprising:
a plurality of inner leads electrically connected to a surface electrode of a semiconductor pellet having a field effect transistor on a principal surface thereof;
a connecting portion for electrically connecting the surface electrode of the semiconductor pellet and the inner leads;
a resin encapsulant formed by encapsulating the semiconductor pellet and the inner leads with resin;
a plurality of outer leads connected to the inner leads and protruding in parallel from the same lateral surface of the resin encapsulant; and
a header bonded to a surface of the semiconductor pellet opposite to the principal surface and having a header protruding portion protruding from a lateral surface of the resin encapsulant opposite to the lateral surface from which the outer leads protrude, wherein
a surface of the header opposite to the surface thereof bonded to the semiconductor pellet is exposed from the resin encapsulant; and
the outer leads are bent.
Since the header is provided with the header protruding portion, the area of the header can be significantly increased to release a significant part of heat generated at the semiconductor pellet through the header having the header protruding portion.
This makes it possible to reduce the thermal resistance of the semiconductor device further.
According to the invention, there is further provided a semiconductor device comprising:
a plurality of inner leads electrically connected to a surface electrode of a semiconductor pellet having a field effect transistor on a principal surface thereof;
a connecting portion for electrically connecting the surface electrode of the semiconductor pellet and the inner leads;
a resin encapsulant formed by encapsulating the semiconductor pellet and the inner leads with resin, a plurality of outer leads connected to the inner leads and protruding in parallel from the same lateral surface of the resin encapsulant; and
a header bonded to a surface of the semiconductor pellet opposite to the principal surface and having a header protruding portion protruding from a lateral surface of the resin encapsulant opposite to the lateral surface from which the outer leads protrude, wherein
a surface of the header opposite to the surface thereof bonded to the semiconductor pellet is an exposed surface exposed from the resin encapsulant;
the outer leads are bent; and
the exposed surface of the header and a mounted surface of the outer leads are provided at substantially the same height.
According to the invention, there is provided a method of manufacturing a semiconductor device comprising the steps of:
providing a semiconductor pellet having a field effect transistor fabricated on a principal surface thereof and formed in a compact plate-like configuration;
providing a lead frame to which a plurality of inner leads and outer leads connected to the respective inner leads are coupled;
providing a header formed in a plate-like configuration using a material having preferable electrical and thermal conductivity;
mechanically and electrically connecting each of the inner leads to the semiconductor pellet with a connecting portion constituted by a protruding terminal at the inner lead or the semiconductor pellet;
mechanically and electrically connecting a surface of the semiconductor pellet opposite to the principal surface to the header;
forming a resin encapsulant by encapsulating the semiconductor pellet, the inner leads and a part of the header with resin; and
bending the plurality of outer leads in a gull wing configuration.
According to the invention, there is provided a method of manufacturing a semiconductor device comprising the steps of:
providing a semiconductor pellet having a field effect transistor fabricated on a principal surface thereof;
providing a lead frame to which a plurality of inner leads and a plurality of outer leads electrically connected to the respective inner leads are coupled;
providing a header formed in a plate-like configuration;
electrically connecting the inner leads and a surface electrode of the semiconductor pellet with a connecting portion constituted by a protruding terminal at the inner lead or the semiconductor pellet;
bonding the header and a surface of the semiconductor pellet opposite to the principal surface;
encapsulating the semiconductor pellet, the inner leads and a part of the header with resin to form a resin encapsulant from which a surface of the header opposite to the surface thereof bonded to the semiconductor pellet is exposed and from which a header protruding portion protrudes in the direction opposite to the protruding direction of the outer leads; and
bending the plurality of outer leads.